Des Moines, Iowa - Nikki Haley and Ron DeSantis pitched Republicans Wednesday on their bids to be the 2024 presidential candidate in the final debate before nominating begins – but spurned repeated chances to make the case for abandoning front-runner Donald Trump.

The head-to-head showdown in Iowa capital Des Moines came five days before the state's pivotal opening vote in the primary season, considered crucial for winnowing the field and giving those left standing a springboard for the rest of the race.

Trump has a commanding lead despite the multiple legal challenges he faces, but has skipped the televised debates, concluding he has nothing to gain by taking prime-time hits from lower-polling rivals.

With no other candidate qualifying and the contest's most vocal Trump critic, Chris Christie, dropping out hours earlier, the pair were expected to go after the ex-president more directly than in previous debates.

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But it quickly became clear that they were competing to be the absent former president's closest runner-up in Iowa rather than looking to eat into his lead as they ducked repeat opportunities to criticize him.

DeSantis, Florida's governor and a hardline conservative, set the tone early on by calling Haley a "mealy-mouthed politician who just tells you what she thinks you want to hear."

"Donald Trump is running to pursue his issues. Nikki Haley is running to pursue her donors' issues. I'm running to pursue your issues and your family's issues and to turn this country around," he said, dusting off a favorite campaign line.

Haley, a former South Carolina governor, hit out at DeSantis' runaway campaign spending and repeatedly directed viewers to a website dedicated to enumerating all of her opponent's "lies."

"Every time he lies... don't turn this into a drinking game because you will be over-served by the end of the night," she said.

The pair spent much of the debate on alternating monologues rehearsing prepared opposition research, aggressively trading barbs on their records and policies running their states.

DeSantis is seeking to regain ground lost to Haley and his path to the nomination depends on a strong showing in Iowa.

Haley is looking to outperform expectations in the Midwestern state and ride into a one-on-one match-up with Trump in her preferred battleground of New Hampshire.

But much of the campaign has been overshadowed by the legal woes facing Trump, who has sought to use the precincts of courthouses across the country to dominate TV coverage and rally support.

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The tycoon's character came up early on, but Haley stuck to the script, repeating a rote campaign remark that he was "the right president at the right time" but that "his way is not my way."

She briefly criticized Trump over his bogus claims that the 2020 election was stolen and for defending the 2021 assault on the US Capitol, but obfuscated when asked if she thought he viewed the Constitution differently from her.

DeSantis was tougher on Trump and hit out at what he characterized as the front-runner's poor record on curbing public disorder, broken promises on border policy, and failure to attack Washington corruption.

But he quickly pivoted back each time to standard campaign lines attacking Haley.

The Iraq veteran, who has promised to have drug smugglers shot dead at the Southern border, focused on his opponent’s record on controlling immigration, taxation, education, and for being soft on abortion.

Haley accused the more isolationist DeSantis of flip-flopping on aid to war-torn Ukraine, called him out repeatedly over his "demeaning" tone, and attacked him over a feud with Disney that cost Florida 2,000 jobs.

Trump, who often arranges "counterprogramming" to draw attention away from the debates, was taking part in a Fox News town hall event elsewhere in Des Moines, his first live appearance on the network in two years.

He said DeSantis would be "working in a pizza shop or perhaps a law firm" without Trump's help with his career.

He sought to assuage fears that he will abandon the rule of law if he is returned to the White House, assuring viewers he was "not going to be a dictator."

"I'm going to manage like we did," he added. "We were so successful, that the country was coming together."